Peritoneal dialysis therapy has drawn greater attention than conventional dialysis using an artificial kidney because of a smaller and simpler form of system including equipment and instrument, a lower cost of treatment, possible prevention of abdominal adhesion, and a reduced burden to the patient.
Among the different versions of peritoneal dialysis, continuous ambulatory peritoneal dialysis often abbreviated as CAPD is regarded most promising because the patient himself or herself can replace a container or bag of dialysis fluid anywhere at home or office, assisting him or her in resuming work.
In the practice of CAPD, a catheter tube is left in the abdominal cavity of the patient, a transfer tube is connected to an outside end of the catheter tube, and a bag tube of an infusion bag full of dialysis fluid is connected to the transfer tube. Then the dialysis fluid is infused from the bag into the abdominal cavity through the tubes and catheter. After dialysis is carried out for a predetermined time, the dialysis fluid in the abdominal cavity is drained into a drainage bag through the tubes. The bag tube and the transfer tube are connected through male and female connectors attached to the tube end.
One and two bag systems are known in the CAPD. The one bag system uses one bag which serves both as an infusion bag for dialysis fluid and a drainage bag. This system imposes a trouble to the patient in that the patient must always carry an empty bag which has been an infusion bag and which is to be used as a drainage bag at the end of dialysis. The two bag system includes a parallel connection (known as a Y set) of an infusion bag for dialysis fluid and a drainage bag. This system allows the infusion and drainage bags to be separated from the transfer tube during dialysis, eliminating a need for carrying a bag.
Since the CAPD is a medical treatment to the abdominal cavity, that is, a site having no protection against bacteria, it is the most critical task to prevent bacterial entry into the respective tubes. Bacterial entry into the tubes can most often occur during connection and disconnection of the transfer tube and the bag tube. An important problem associated with the two bag system in which the bag tube is disconnected from the transfer tube during dialysis is how to prevent bacterial entry from the open end of the transfer tube.
For the prevention of bacterial entry, Japanese Patent Disclosure No. 500801/1984 corresponding to PCT/US83/00511 (based on U.S. application Ser. No. 378,315 filed May 14, 1982, (now U.S. Pat. No. 4,440,207) discloses an antibacterial protective cap adapted to mount on a connector. The cap includes two large and small continuous chambers adapted to accommodate the mating portion of a connector attached to the tube end. The outer large chamber on the inner wall is lined with an absorbent material carrying a disinfectant thereon. The key is to place the mating portion of the connector in contact with the disinfectant. This concept achieves a low level of sterilization by carrying out mere disinfection in the sense that disease-inducing bacteria are reduced or attenuated rather than a high level of sterilization capable of maintaining a sterile condition in the sense that all bacteria are completely killed. Iodide agents such as Isodine (trade mark, Meiji Seika K.K.) and povidone-iodine are often used as the disinfectant. Since the disinfectant, when mixed with the dialysis fluid, acts as a harmful substance to the human body, it must be diluted to a fully low concentration, resulting in lower biocidal activity. Therefore, the cap cannot completely prevent bacterial entry into the tube, leaving a safety problem.